I tried to call back the number (02) 9067 0541 but the person who picked up the phone disconnected the call

This is a number verification IVR which is used to determine if the phone number it dialled (your phone number) actually exist. If so, then it puts it into its database for follow up calls later. I quickly blocked it.

The caller registers this number (02) 9067 0541 on my phone on the 4th January 2021, 6PM Melbourne (VIC) time. Possibly h**ker looking to gain something, hiding behind or under his/her "mother's" thingy.